The field of the invention is boot and shoe making and the present invention is concerned with the combination of a lasted upper with a unitsole during the molding of the unitsole.
The state of the art of integrally molding a shoe sole to an upper may be ascertained by reference to U.S. Pat. No. 4,034,431, the disclosure of which is incorporated herein. With particular reference to FIGS. 36, 37, 68, 70a, 70b, 72-74, 77 and 83 of U.S. Pat. No. 4,034,431, it can be seen that the upper is molded and connected to a shoe sole in an injection molding cavity by flowing molten resinous material which forms the sole around connecting portions of lateral side sections of the upper.
Shoe unitsoles, such as those shown in applications Ser. Nos. 919,583 and 21,299, are mass produced on a machine disclosed in a brochure entitled "Spare Parts list for Type F--Machine and Periphery Machinery PA20" published March 1976 and supplied by Elastogran Maschenenbau GmbH & Co., Polyurethan-Gruppe der BASF, Mitterstrasseweg, Stasslach vor Muenchen, West Germany. In this machine, unitsole molds are located in stations within an outer circle of about 20 feet in diameter. A metering arm is pivoted for rotation in the middle of the circle and delivers given amounts of a mixture of isocyanate and polyol to each molding station in succession. After delivery of the isocyanate-polyol mixture to a bottom mold, the metering arm is rotated to the next station, the open mold with expanding polyurethane resin is covered with a top mold and while the next mold is being filled, the exothermic reaction of the isocyanate-polyol cures and forms the unitsole within 5 minutes.
A suitable commercial isocyanate-polyol composition useful with the Type F--Machine and Periphery Machinery PA20 and with the present invention is a product of the Mobay Chemical Co. designated BAYFLEX 230. This commercial isocyanatepolyol composition uses approximately 38.5 parts per weight of MONDUR BF to approximately 100 parts per weight of BAYFLEX 230 poly(oxyalkylene) polyol to form the foamed polyurethane unitsoles. The polyurethane unitsoles are foamed to a specific gravity of 0.35-0.60 in approximately 3-3.5 minutes at a temperature of about 125.degree.-135.degree. F. and a pressure of about 10-40 lbs per square inch is generated by the exothermic reaction.
Other foamed resins besides polyurethane are useful in the present invention such as foaming epoxy, polyester and polyvinyl resins. The state of the art of foamed plastics may be ascertained by reference to the Kirk-Othmer, "Encyclopedia of Chemical Technology", Second Edition, Vol. 9 (1966), pp. 847-884 under the section Foamed Plastics and Vol. 21 (1970) pp. 56-106 under the section Urethane Polymers the disclosures of which are incorporated herein.
The prior art method of direct molding an upper to a shoe sole as disclosed by U.S. Pat. No. 4,034,431 requires the use of injection molding apparatus with the resulting expense of metal conforming molds for each shoe design and size.